I. Field
The present invention relates generally to power transmission systems. More specifically, the present invention relates to methods and circuits for wirelessly transferring power.
II. Description of Related Art
In portable electronics, a wireless power transmission circuit may be utilized to charge a portable device. For example, an electronic toothbrush system may include a portable toothbrush and a charging base into which the portable toothbrush is placed to facilitate charging a battery in the toothbrush. In such system, inductive or magnetic coupling may be utilized to transfer power from a primary inductor in the charging base to a secondary inductor in the portable toothbrush.
Each of the primary and secondary inductors typically corresponds to a coil, where the turns ratio between the inductors may be N:1 or 1:N, where N is an integer number greater than zero. The number of turns for the primary and secondary inductors is selected to provide a mutual inductance sufficiently high so as to provide the desired amount of power to the portable device.
In many portable devices, space is a premium. As such, the gauge of wire selected for the inductor may be reduced to reduce the size of the inductor. The reduction in gauge, however, tends to increase the resistance of the inductor, which results in unwanted power loss in the inductor.